nixos/systemd-networkd-vrf: implement working TCP test on a 5.x kernel #94369
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By design, VRFs allow route-leaking for forwarded packages, but not for local processes using a socket. While it was possible to leak such TCP traffic through a VRF on a 4.x kernel, this behavior was considered wrong and got fixed in Linux 5.x[1]. From now on, local unix sockets must run in the VRF itself using `ip vrf exec`[2] which basically injects a BPF program into the VRF and drops elevated networking capabilities by default for the specified command. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3c82a21f4320c8d54cf6456b27c8d49e5ffb722e [2] https://man7.org/linux/man-pages/man8/ip-vrf.8.html
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@GrahamcOfBorg test systemd-networkd-vrf |
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Motivation for this change
By design, VRFs allow route-leaking for forwarded packages, but not for
local processes using a socket. While it was possible to leak such TCP
traffic through a VRF on a 4.x kernel, this behavior was considered
wrong and got fixed in Linux 5.x[1].
From now on, local unix sockets must run in the VRF itself using
ip vrf exec[2] which basically injects a BPF program into the VRF anddrops elevated networking capabilities by default for the specified
command.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3c82a21f4320c8d54cf6456b27c8d49e5ffb722e
[2] https://man7.org/linux/man-pages/man8/ip-vrf.8.html
Things done
sandboxinnix.confon non-NixOS linux)nix-shell -p nixpkgs-review --run "nixpkgs-review wip"./result/bin/)nix path-info -Sbefore and after)